Use libtool "noinst" local helper libs and use one Makefile.am per
subdir, which is the usual/preferred method. These helper libraries are
purely local and will not be installed.
This also fixes out-of-tree builds of sigrok, i.e. building in a
directory other than the sigrok source directory, e.g.
$ cd /home/user
$ git clone ...sigrok
$ cd sigrok
$ ./autogen.sh
$ mkdir /tmp/foo
$ cd /tmp/foo
$ /home/user/sigrok/configure
$ make
$ make install
This will place all build results (.o files, .la files, etc) in the
local build directory (/tmp/foo) instead of the source directory
(/home/user/sigrok in this example). The installation directory is
selected via the --prefix configure option (/usr/local per default).
We have SIGROK_OK for functions calls where no errors occured. All
error code names start with SIGROK_ERR and are globally unique,
negative values.
The value SIGROK_ERR is a generic/unspecified error code, all others,
such as SIGROK_ERR_MALLOC, refer to a specific error condition.
This commit renames the old SIGROK_NOK etc.